BEIJING - Following a successful launch on Tuesday morning, the unmanned Shenzhou VIII spacecraft was sent on its way to the country's first rendezvous and docking exercise to be held overnight,Wednesday to Thursday, space officials said.

A Long March II-F rocket blasted off from the Jiuquan Satellite Launch Center in Northwest China's Gansu province at 5:58 am as planned, lofting the Shenzhou VIII spacecraft into an initial orbit with a perigee of 200 km and an apogee of 329 km above Earth nine minutes later.

Chang Wanquan, chief commander of China's manned space program, announced the successful launch at around 6:19 am.

Vice-Premier Zhang Dejiang watched the blastoff on site. Senior officials from the European Space Agency and the German Aerospace Center also witnessed the launch at the Jiuquan facility.

Zhang Dejiang said that the successful launch signals China's taking a key step closer to its first space docking.

The spacecraft is set to rendezvous and dock with Tiangong-1 space module around Thursday midnight, according to the Beijing Aerospace Control Center.

Zhang Bonan, chief designer of the spacecraft, said the process is full of risks.

Compared to the previous spacecraft, the 9-meter-tall Shenzhou VIII is equipped with radars and optical sensors for rendezvous and complicated devices for docking.

The radars and optical sensors will guide the spacecraft to bridge its distance with Tiangong-1, from 10,000 km to only a little more than 10 centimeters.

"Many devices such as optical sensors cannot be fully tested on Earth," he said, explaining it was the first time such devices were being used in outer space.

Shenzhou VIII will make four stops at 5 km, 400 meters, 140 meters and 30 meters behind Tiangong-1 during the rendezvous, so that the controllers can double check the two vessels' positions, said Ma Yongping, deputy director of the Beijing center.

The docking port on the front of its orbital module is the country's most complicated space device so far, he said.

"The docking port has more than 10,000 small parts, including some 300 bearings and 300 gear wheels. This places high demands on the spacecraft's control system," he said.

Engineers have nearly 100 responses planned to cope with possible emergencies.

If all goes according to plan, the two vessels will fly as one for 12 days before separating and docking again on Nov 14. They will orbit together for two more days and separate on Nov 16. The Shenzhou VIII's return capsule is set to return to Earth on Nov 17, according to China National Radio.

Tim Robinson, editor of Aerospace International, told Xinhua News Agency that China's approach to space docking is very different from that practiced by other countries.

"Unlike the United States, which started with manually flown dockings, China is attempting an automated docking," Robinson said.

"This probably reduces the human risk to crew, but it is also very ambitious," Robinson said.

Shenzhou VIII marks China's first international collaboration as regards its manned space program, according to Wu Ping, the program spokeswoman.

She said that scientists of China and Germany will together conduct 17 experiments on life sciences. A joint Chinese-German payload was placed inside Shenzhou VIII's return capsule. Samples including plant seeds will be exposed to microgravity and space radiation for more than two weeks.

"The future Chinese space station will be open to scientists from the world," said Zhou Jianping, chief designer of China's manned space program.

China will send vehicles Shenzhou IX and Shenzhou X on two more docking missions in 2012. At least one of the two will carry astronauts, possibly include women.